extension

/ɪkˈstɛnʃən/

//ɪkˈstɛnʃən// noun

By · According to Wiktionary data (CC BY-SA) ·

"extension" is a 9-letter English headword indexed on PlainSpell.

The verdict

“extension” is a regularly-used English word, ranked #3,231 in English word frequency and used as a noun.

#3,231
frequency rank, English
9
letters
14
tracked misspellings
3
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - The act of extending; a stretching out; enlargement in length, breadth, or time; an increase.

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

extension vs extensive
78% similar
extension vs extrusion
78% similar
extension vs expansion
78% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for extension
PropertyValue
Headwordextension
LanguageEnglish
Part of speechNoun
IPA/ɪkˈstɛnʃən/
Letters9
Frequency rank#3,231
Misspellings tracked14
Confusable pairs3
SourceWiktionary (kaikki.org)

Where “extension” sits in English frequency

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right). extension lands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

Spelling & Dictionary Insight

The English entry for extension is 9 letters long, classified as a noun, and transcribed in the International Phonetic Alphabet as /ɪkˈstɛnʃən/. Corpus data places it at rank #3,231 in overall English word frequency, indicating it appears regularly in written and spoken text. Wiktionary records 21 distinct senses for this headword, so context determines which meaning a reader should apply.

Our generated misspelling index lists 14 likely wrong-spelling variants for extension, with forms such as "etxension", "exetnsion", and "extenison". Each of these forms differs from the correct spelling by one small edit: a doubled letter, a dropped silent letter, or a substituted vowel. It also participates in 3 confusable-pair relationships, "extensive", "extrusion", "expansion", a pairing that trips writers up because the two words share enough sound or shape to blur together.

Etymologically, the entry records: From Middle English extensioun, from Old French estension, from Latin extensiō, extensiōnem. The correct English form is extension, spelled E-X-T-E-N-S-I-O-N.

Definition

  1. 1
    The act of extending; a stretching out; enlargement in length, breadth, or time; an increase.
  2. 2
    The state of being extended.
  3. 3
    That property of a body by which it occupies a portion of space (or time, e.g. "spatiotemporal extension").
  4. 4
    A short exact sequence 1→H→E→G→1, or the group E therein.
  5. 5
    A short exact sequence 0→B→E→A→0, or the object E therein.
  6. 6
    A part of a building that has been added onto the original.
  7. 7
    An outgrowth; a part of something that extends its capabilities.
  8. 8
    Capacity of a concept or general term to include a greater or smaller number of objects; — correlative of intension.
  9. 9
    semantic widening, broadening of meaning
  10. 10
    A written engagement on the part of a creditor, allowing a debtor further time to pay a debt.
  11. 11
    The operation of stretching a broken bone so as to bring the fragments into the same straight line.
  12. 12
    An exercise in which an arm or leg is straightened against resistance.
  13. 13
    A simple offensive action, consisting of extending the weapon arm forward.
  14. 14
    A numerical code used to indicate a specific telephone in a telecommunication network.
  15. 15
    Ellipsis of file extension.
  16. 16
    An optional software component that adds functionality to an application.
  17. 17
    The set of tuples of values that, used as arguments, satisfy the predicate.
  18. 18
    A kind of derivative morpheme applied to verbs in Bantu languages.
  19. 19
    The ideal in the codomain generated by the image of the given ideal under the given homomorphism.
  20. 20
    University programs that are targeted at the broader (usually adults) community whose participants are not full-time enrolled students.
  21. 21
    Clipping of hair extension, nail extension, or eyelash extension.

Etymology

From Middle English extensioun, from Old French estension, from Latin extensiō, extensiōnem.

Synonyms

denotation

Antonyms

shorteninglimitationcurl

This word in other languages

extensión(Español)extension(Français)Ausdehnung(Deutsch)extensão(Português)

Common misspellings

Also misspelled as: etxension,exetnsion,extenison,extennsion,extensino,extensionn,extensoin,extenssion,extention,extesnion,extnesion,exttension,exxtension,xetension

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of extension - expressed in single-character edits (insert, delete, or swap one letter). Bigger bars stand out at a glance; a one-edit slip is the hardest to catch.

etxension2exetnsion2extenison2extennsion1extensino2extensionn1extensoin2extenssion1
Edit distance from "extension"

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "extension"?
"extension" is spelled E-X-T-E-N-S-I-O-N. The IPA pronunciation is /ɪkˈstɛnʃən/.
What does "extension" mean?
As a noun, "extension" means: The act of extending; a stretching out; enlargement in length, breadth, or time; an increase.
What words are commonly confused with "extension"?
"extension" is commonly confused with "extensive", "extrusion", "expansion". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "extension"?
The IPA (International Phonetic Alphabet) transcription for "extension" is /ɪkˈstɛnʃən/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "extension"?
From Middle English extensioun, from Old French estension, from Latin extensiō, extensiōnem. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Using “extension”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is E-X-T-E-N-S-I-O-N - every other letter order is a misspelling in standard orthography.
  • Say it as /ɪkˈstɛnʃən/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
  • Don't mix it up with “extensive” - see the side-by-side comparison. extension vs extensive
  • Browse more English words and confusable pairs in the same reference. English words
Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list